In recent years, soft silicone hydrogel contact lenses, for example, Focus NIGHT & DAY™ and O2OPTIX™ (CIBA VISION), and PureVision™ (Bausch & Lomb) become more and more popular because of their high oxygen permeability and comfort. “Soft” contact lenses conform closely to the shape of the eye, so oxygen cannot easily circumvent the lens. Soft contact lenses must allow oxygen from the surrounding air (i.e., oxygen) to reach the cornea because the cornea does not receive oxygen from the blood supply like other tissue. If sufficient oxygen does not reach the cornea, corneal swelling occurs. Extended periods of oxygen deprivation cause the undesirable growth of blood vessels in the cornea. By having high oxygen permeability, a silicone hydrogel contact lens allows sufficient oxygen permeate through the lens to the cornea and to have minimal adverse effects on corneal health.
However, a silicone hydrogel material typically has a surface or at least some areas of its surface which is hydrophobic (non-wettable). Lipids or proteins from the ocular environment can be adsorbed onto hydrophobic surface or surface areas of a silicone hydrogel contact lens. The hydrophobic surface or surface areas of a silicone hydrogel contact lens may cause it be adhered to the eye. Thus, a silicone hydrogel contact lens will generally require a surface modification to increase surface hydrophilicity.
A known method for modifying the hydrophilicity of a relatively hydrophobic contact lens material is to attach hydrophilic polymers onto contact lenses according to various mechanisms (see for example, U.S. Pat. Nos. 6,099,122, 6,436,481, 6,440,571, 6,447,920, 6,465,056, 6,521,352, 6,586,038, 6,623,747, 6,730,366, 6,734,321, 6,835,410, 6,878,399, 6,923,978, 6,440,571, and 6,500,481, US Patent Application Publication Nos. 2009/0145086 A1, 2009/0145091A1, 2008/0142038A1, and 2007/0122540A1, all of which are herein incorporated by reference in their entireties). Although those techniques can be used in rendering a silicone hydrogel material wettable, they may not be cost-effective and/or time-efficient for implementation in a mass production environment, because they typically require relatively long time and/or involve laborious, multiple steps to obtain a hydrophilic coating.
Therefore, there is a need for a method of applying hydrophilic coating to a silicone hydrogel contact lens in a cost-effective and time-efficient manner.